Processes for producing aldehydes by the hydroformylation of olefins in the presence of a catalyst have been known and have been commercialized all over the world.
There are many known documents concerning those hydroformylation reactions, and the pressures in industrial hydroformylation reactions have usually been about from 2 MPaG to 20 MPaG and are about 1 MPaG even in the case of reduced-pressure processes. Consequently, C3 and C4 olefins under such industrial pressures have generally been fed as a liquid to the reactor because these olefins are liquid at ordinary temperature and a pressure of about 1 MPaG (see patent documents 1 to 3).
However, it was found that in a reactor to which a liquid olefin is continuously fed, the liquid level in the reactor is not stable under certain conditions and this may result in a behavior which is too unstable to control the progress of the hydroformylation reaction.
The causes for such troubles are thought to include the following: the feedstock olefin begins to increase in temperature in the reactor and gasifies abruptly; and the feedstock olefin comes to be present in excess locally and this causes a local reaction. The fluctuations in liquid level in the reactor are presumed to have occurred as a result of these.
Those unstable behaviors not only lower the yield in the target hydroformylation reaction but also make it impossible to control the liquid level in the reactor and the temperature. Efficient production cannot hence be realized.
[Patent Document 1] JP-A-61-218546
[Patent Document 2] JP-A-3-204831
[Patent Document 3] JP-A-52-125103